Williams fractures ankle, could be lost for season

Starting nose tackle Ian Williams reportedly broke his left ankle on the 49ers’ second defensive series, a league source confirmed.

A 49ers spokesman only would say that Williams indeed has an ankle injury but would not comment on the severity.

Glenn Dorsey replaced Williams and produced a sack on the next series. Williams, an undrafted free agent in 2011 out of Notre Dame, had beaten out Dorsey this offseason and training camp for the starting nose tackle job.

Williams hopped off the field without putting weight on it while being aided by trainers.